In the past, welding tools have been cooled, during an actual welding operation, in order to dissipate heat from the welded area of an item. That type of cooling, however, does not permit complete equalization of temperature in the welded area of the item, especially where such items are made from a relatively thick material, such as plastic, having poor heat-conducting properties. If temperature equalization is not achieved, any resulting temperature difference existing in the material after the welding operation may be sufficient to cause shrinkage deformation, even though the peak value of the temperature was lowered by direct cooling in the welding tool during the welding operation.